The present invention relates to a scroll fluid machine, in which a refrigerant, air, or other compressible gases work, and specifically is preferable to be applied to scroll compressors of a cantilever bearing support construction used in refrigerating/air-conditioning equipment.
Scroll compressors are widely used, as compressors for refrigerating/air-conditioning equipment, in various fields, and are superior in efficiency, reliability and calmness to compressors of other systems.
As a conventional scroll fluid machines, there is one disclosed in, for example, JP-A-8-121366. A seal member is provided between an orbiting scroll member and a frame, and a backpressure chamber is formed on an opposed side of the orbiting scroll member to a wrap. The backpressure chamber comprises, on account of the seal member, a first space disposed centrally to be under pressure substantially equal to a discharge pressure, and a second space disposed on an outer peripheral side to be maintained at an intermediate pressure between a suction pressure and the discharge pressure. Lubricating oil accumulated at a bottom of a closed vessel is conducted to the first space and the second space is communicated through a small hole to a compression space in the course of compression. Also, the first space is communicated to a compressor bottom side via a drain oil path or a drain oil pipe to return the lubricating oil in the backpressure chamber to the bottom in the closed vessel.
JP-A-60-224988 describes a scroll fluid machine, in which a concave, annular chamber is provided on a side of an orbiting scroll close to a frame, a seal surface is provided on the frame opposed to the chamber, and a seal ring is provided in the annular chamber to divide backpressure chamber into a pressure chamber in a central region and a low-pressure chamber in an outer peripheral region. Also, gaps are provided between the orbiting scroll and the frame and between the seal ring and a bottom of the annular chamber to allow axial movements of the orbiting scroll, and the gap between the seal ring and the bottom of the annular chamber is communicated to the pressure chamber to prevent generation of an excessive containment pressure while an improvement in sealing quality of the seal ring is contemplated.
JP-A-8-93664 describes a scroll compressor, in which a balance weight is arranged in a backpressure chamber and which is of a cantilever bearing construction.
The conventional techniques take no sufficient account of entrainment of lubricating oil into a working fluid, which is sucked and compressed. In particular, with the arrangement, in which the balance weight is arranged in the backpressure chamber to provide for a cantilever bearing construction, oil for lubrication of a shaft support of an orbiting scroll member and a shaft support for a crankshaft is mixed with a working fluid having passed through a suction port, the lubricating oil of high-temperature heats the working fluid being compressed, and the working fluid solved into the lubricating oil bubbles and is recompressed together with the working fluid in the course of compression, whereby oil heating leakage loss is increased to cause a decrease in energy efficiency.
It is an object of the invention to provide a scroll fluid machine, in which entrainment of lubricating oil into a working fluid being sucked and compressed can be decreased and which can realize a cantilever bearing construction.
It is a further object of the invention to eliminate direct mixing of oil, which lubricates a shaft support of an orbiting scroll member and a shaft support for a crankshaft, with a working fluid having passed through a suction port, prevent heating of the working fluid by the lubricating oil during compression, and to decrease that oil heating leakage loss, which the working fluid solved into the lubricating oil bubbles and is recompressed into a working refrigerant in the course of compression to cause, to obtain a high energy efficiency.
It is a still further object of the invention to eliminate direct mixing of a working fluid and lubricating oil and to realize a small loss of oil via mixing (an amount of oil, which is carried outside a compressor together with a discharged gas).
It is a further object of the invention to improve reliability in shaft supports by equalizing pressures on the shaft supports substantially to a discharge pressure to suppress breakage of oil films conventionally generated on the shaft supports and caused by bubbling of a refrigerant.